RNA differs from DNA in several key ways. RNA is typically single-stranded, contains ribose sugar instead of deoxyribose, and contains uracil instead of thymine. There are multiple types of RNA that serve different cellular functions, including messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA). mRNA carries coding information from DNA to the ribosome for protein synthesis. tRNA transfers amino acids to the ribosome during protein assembly according to the mRNA codon sequence. rRNA is a core component of ribosomes and facilitates protein translation.

1. 1

2. RNA (RIBONUCLEIC
ACID )
RNA is a
polymer of
ribonucleoti
des linked
together by
3’-5’
phosphodies
ter linkage
2

3. RNA VS DNA
3

4. 4
DIFFERENCES BETWEEN RNA AND
DNA
S.No. RNA DNA
1) Single stranded mainly
except when self
complementary sequences
are there it forms a double
stranded structure (Hair
pin structure)
Double stranded (Except
for certain viral DNA s
which are single
stranded)
2) Ribose is the main sugar The sugar moiety is
deoxy ribose
3) Pyrimidine components
differ. Thymine is never
found(Except tRNA)
Thymine is always there
but uracil is never found
4) Being single stranded
structure- It does not
follow Chargaff’s rule
It does follow Chargaff's
rule. The total purine
content in a double
stranded DNA is always
equal to pyrimidine

5. 5
DIFFERENCES BETWEEN RNA AND
DNA
S.No. RNA DNA
5) RNA can be easily
destroyed by alkalies to
cyclic diesters of mono
nucleotides.
DNA resists alkali action
due to the absence of
OH group at 2’ position
6) RNA is a relatively a
labile molecule,
undergoes easy and
spontaneous
degradation
DNA is a stable
molecule. The
spontaneous
degradation is very
slow. The genetic
information can be
stored for years
together without any
change.
7) Mainly cytoplasmic,
but also present in
nucleus (primary
transcript and small
Mainly found in
nucleus, extra nuclear
DNA is found in
mitochondria, and

6. 6
DIFFERENCES BETWEEN RNA AND
DNA
S.No. RNA DNA
9) There are various types of
RNA – mRNA, r RNA, t
RNA, Sn RNA, Si
RNA, mi RNA and hn RNA.
These RNAs perform
different and specific
functions.
DNA is always of one type
and performs the
function of storage and
transfer of genetic
information.
10) No variable physiological
forms of RNA are found.
The different types of
RNA do not change their
forms
There are variable
forms of DNA (A to E
and Z)
11) RNA is synthesized from
DNA, it can not form
DNA(except by the action
of reverse transcriptase). It
can not duplicate (except
DNA can form DNA by
replication, it can also
form RNA by
transcription.

7. TYPES OF RNA
In all prokaryotic and eukaryotic
organisms, three main classes of RNA
molecules exist-
1) Messenger RNA(m RNA)
2) Transfer RNA (t RNA)
3)Ribosomal RNA (r RNA)
The other are –
o small nuclear RNA (SnRNA),
o micro RNA(mi RNA) and
o small interfering RNA(Si RNA) and
o heterogeneous nuclear RNA (hnRNA).

8. MESSENGER RNA (M-
RNA)
Comprises only 5% of the RNA in the
cell
Most heterogeneous in size and base
sequence
All members of the class function as
messengers carrying the information in

9. STRUCTURAL
CHARACTERISTICS OF M-
RNA
The 5’ terminal end is capped by 7-
methyl guanosine triphosphate cap.
The cap is involved in the
recognition of mRNA by the
translating machinery
It stabilizes m RNA by protecting it
from 5’ exonuclease

10. STRUCTURAL
CHARACTERISTICS OF M-
RNA(CONTD.)
The 3’end of most m-RNAs have a polymer
of Adenylate residues( 20-250)
 The tail prevents the attack by 3’
exonucleases
Histones and interferons do not contain poly
A tails
On both 5’ and 3’ end there are non coding
sequences which are not translated (NCS)
The intervening region between non coding
sequences present between 5’ and 3’ end is
called coding region. This region encodes for

11. STRUCTURAL
CHARACTERISTICS OF M-
RNA
5’ cap and 3’ tail impart stability to m RNA by
protecting from specific exo nucleases.

12. STRUCTURAL
CHARACTERISTICS OF M-
RNA(CONTD.)
The m- RNA molecules are formed with
the help of DNA template during the
process of transcription.
The sequence of nucleotides in m RNA is
complementary to the sequence of
nucleotides on template DNA.
The sequence carried on m -RNA is read in
the form of codons.
A codon is made up of 3 nucleotides
The m-RNA is formed after
processing of heterogeneous
nuclear RNA

13. HETEROGENEOUS
NUCLEAR RNA (HNRNA)
In mammalian nuclei ,hnRNA is the
immediate product of gene
transcription
The nuclear product is heterogeneous in
size (Variable) and is very large.
Molecular weight may be more than 107,
while the molecular weight of m RNA is
less than 2x 106
75 % of hnRNA is degraded in the
nucleus, only 25% is processed to
mature m RNA

14. Heterogeneous nuclear RNA (hnRNA)
Mature m –RNA is formed from primary transcript by capping,
tailing, splicing and base modification.

15. TRANSFER RNA (T-
RNA)
Transfer RNA are the smallest of three major
species of RNA molecules
They have 74-95 nucleotide residues
They are synthesized by the nuclear
processing of a precursor molecule
They transfer the amino acids from
cytoplasm to the protein synthesizing
machinery, hence the name t RNA.
They are easily soluble , hence called “Soluble
RNA or s RNA
They are also called Adapter molecules, since
they act as adapters for the translation of the
sequence of nucleotides of the m RNA in to
specific amino acids
There are at least 20 species of t RNA one

16. STRUCTURAL CHARACTERISTICS
OF T- RNA
1)Primary structure- The nucleotide
sequence of all the t RNA molecules allows
extensive intrastand complimentarity that
generates a secondary structure.
2)Secondary structure- Each single t- RNA
shows extensive internal base pairing and
acquires a clover leaf like structure. The
structure is stabilized by hydrogen
bonding between the bases and is a
consistent feature.

17. STRUCTURAL
CHARACTERISTICS OF T-
RNA
Secondary structure (Clover leaf
structure)
All t-RNA contain 5 main arms
or loops which are as follows-
a) Acceptor arm
b) Anticodon arm
c) D HU arm
d) TΨ C arm
e) Extra arm

18. SECONDARY STRUCTURE OF
T- RNA
The carboxyl group of amino acid is attached to 3’OH group of
Adenine nucleotide of the acceptor arm. The anticodon arm
base pairs with the codon present on the m- RNA

19. SECONDARY STRUCTURE OF
T- RNA
a)Acceptor arm
 The acceptor arm is at 3’ end
 It has 7 base pairs
 The end sequence is unpaired
 Cytosine, Cytosine-Adenine at the 3’
end
 The 3’ OH group terminal of Adenine
binds with carboxyl group of amino
acids
 The t RNA bound with amino acid
is called Amino acyl t RNA
 CCA attachment is done post

20. SECONDARY STRUCTURE OF T-
RNA(CONTD.)
b) Anticodon arm
Lies at the opposite end of acceptor arm
5 base pairs long
Recognizes the triplet codon present in
the m RNA
Base sequence of anticodon arm is
complementary to the base sequence of m
RNA codon.
Due to complimentarity it can bind
specifically with m RNA by hydrogen bonds.

21. SECONDARY STRUCTURE OF T-
RNA(CONTD.)
c) DHU arm
It has 3-4 base pairs
Serves as the recognition site for the
enzyme (amino acyl t RNA synthetase) that
adds the amino acid to the acceptor arm.
d) TΨC arm
This arm is opposite to DHU arm
Since it contains pseudo uridine that is
why it is so named
 It is involved in the binding of t RNA to the
ribosomes

22. SECONDARY STRUCTURE OF T-
RNA(CONTD.)
e) Extra arm or Variable arm
About 75 % of t RNA molecules possess a short extra arm
If about 3-5 base pairs are present the t-RNA is said to be
belonging to class 1. Majority t -RNA belong to class 1.
The t –RNA belonging to class 2 have long extra arm, 13-21
base pairs in length.

23. TERTIARY STRUCTURE OF
T- RNA
The L shaped tertiary
structure is formed by
further folding of the
clover leaf due to
hydrogen bonds
between T and D arms.
The base paired
double helical stems
get arranged in to two
double helical
columns, continuous
and perpendicular to
one another.

24. RIBOSOMAL RNA
(RRNA)
The mammalian ribosome contains two
major nucleoprotein subunits—a larger one
with a molecular weight of 2.8 x 106 (60S)
and a smaller subunit with a molecular
weight of 1.4 x 106 (40S).
The 60S subunit contains a 5S ribosomal RNA
(rRNA), a 5.8S rRNA, and a 28S rRNA; there are
also probably more than 50 specific
polypeptides.
The 40S subunit is smaller and contains a
single 18S rRNA and approximately 30
distinct polypeptide chains.
All of the ribosomal RNA molecules except
the 5S rRNA are processed from a single 45S

25. RIBOSOMAL RNA
(RRNA)

26. RIBOSOMAL RNA
(RRNA)
The functions of the ribosomal
RNA molecules in the ribosomal
particle are not fully understood,
but they are necessary for
ribosomal assembly and seem to
play key roles in the binding of
mRNA to ribosomes and its
translation
Recent studies suggest that an rRNA
component performs the peptidyl
transferase activity and thus is an

27. SMALL RNA
Most of these molecules are
complexed with proteins to form
ribonucleoproteins and are
distributed in the nucleus, in the
cytoplasm, or in both.
They range in size from 20 to
300 nucleotides and are present
in 100,000– 1,000,000 copies
per cell.

28. SMALL NUCLEAR RNAS
(SNRNAS)
snRNAs, a subset of the small RNAs,
are significantly involved in mRNA
processing and gene regulation
Of the several snRNAs, U1, U2, U4,
U5, and U6 are involved in intron
removal and the processing of
hnRNA into mRNA
The U7 snRNA is involved in
production of the correct 3' ends of
histone mRNA—which lacks a

29. SMALL NUCLEAR RNAS
(SNRNAS).
Sn RNA s are involved in the process of splicing (intron removal)
of primary transcript to form mature m RNA. The Sn RNA s form
complexes with proteins to form Ribonucleoprotein particles
called snRNPs

30. MICRO RNAS, MIRNAS, AND
SMALL INTERFERING
RNAS, SIRNAS
These two classes of RNAs
represent a subset of small RNAs;
both play important roles in gene
regulation.
miRNAs and siRNAs cause
inhibition of gene expression by
decreasing specific protein
production albeit apparently via
distinct mechanisms

31. MICRO RNAS
(MIRNAS)
miRNAs are typically 21–25
nucleotides in length and are
generated by nucleolytic processing
of the products of distinct
genes/transcription units
The small processed mature miRNAs
typically hybridize, via the formation
of imperfect RNA-RNA duplexes
within the 3'- untranslated regions of
specific target mRNAs, leading via
unknown mechanisms to translation
arrest.

32. SMALL INTERFERING RNAS
(SIRNAS)
siRNAs are derived by the specific nucleolytic
cleavage of larger, double-stranded RNAs to
again form small 21– 25 nucleotide-long
products.
These short siRNAs usually form perfect RNA-
RNA hybrids with their distinct targets
potentially anywhere within the length of the
mRNA where the complementary sequence
exists.
Formation of such RNA-RNA duplexes
between siRNA and mRNA results in reduced
specific protein production because the
siRNA-mRNA complexes are degraded by
dedicated nucleolytic machinery;